But nobody chooses the environment in which they're born into, the propaganda of the era they are subjected to, or the general information publicly available to them during their lives.

I agree here, except that I don't let people off the hook for going with those tendencies rather than against them. At some point people should be allowed to dislike police even if exceptions exist to how police are typically known to act (and those exceptions often have short careers, but I digress), for example.

not the bygone fact that someone lived a better life in the past

If those boomers (and junior boomer Xers) stopped shitting on millennials, zoomers, and whatever-gen-alpha-will-be-called, it'd be easier to not fling some of it back. I can't blame people for resenting the sheer arrogance of materially privileged people LARPing as born-better rugged individuals that were just better than the entitled youths nowadays.